#pragma once
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <unordered_map>
#include <mutex>
#include "util.hpp"
namespace ns_index
{
    struct DocInfo
    {
        std::string title;   // 文档的标题
        std::string content; // 文档对应的去标签之后的内容
        std::string url;     // 官网文档的url
        u_int64_t doc_id;
    };
    struct InvertedElem
    {
        u_int64_t doc_id;
        std::string words;
        int weight;
    };
    // 倒排拉链
    typedef std::vector<InvertedElem> InvertedList;
    class Index
    {
    private:
        // 正派索引的数据结构用数组，数组的下标天然石文档的ID
        std::vector<DocInfo> forward_index;
        // 倒排索引一定是一个关键字和一组（个）InvertedElem对应[关键字和倒排拉链的映射关系]
        std::unordered_map<std::string, std::vector<InvertedElem>> inverted_index;

    private:
        Index() {}
        Index(const Index &) = delete;
        Index &operator=(const Index &) = delete;
        static Index *instance;
        static std::mutex mtx;

    public:
        ~Index() {};

    public:
        static Index *GetInstance()
        {
            if (nullptr == instance)
            {
                mtx.lock();
                if (nullptr == instance)
                {
                    instance = new Index();
                }
                mtx.unlock();
            }

            return instance;
        }
        // 根据doc_id找到文档内容
        DocInfo *GetForwardIndex(const u_int64_t doc_id)
        {
            if (doc_id >= forward_index.size())
            {
                std::cerr << "doc_id out range.error" << std::endl;
                return nullptr;
            }
            return &forward_index[doc_id];
        }
        // 根据关键字string，获取倒排拉链
        InvertedList *GetInvertedList(const std::string &word)
        {
            auto iter = inverted_index.find(word);
            if (iter == inverted_index.end())
            {
                std::cerr << word << "have no InvertedList" << std::endl;
                return nullptr;
            }
            return &(iter->second);
        }
        // 根据文档的去标签格式化之后的文档，构建正排和倒排索引
        bool BuildIndex(const std::string &input)
        {
            std::ifstream in(input, std::ios::in | std::ios::binary);
            if (!in.is_open())
            {
                std::cerr << "sorry." << input << "open error" << std::endl;
                return false;
            }
            std::string line;
            int count = 0;
            while (std::getline(in, line))
            {
                DocInfo *doc = BuildForwardIndex(line);
                if (nullptr == doc)
                {
                    std::cerr << "build：" << line << "error" << std::endl;
                    continue;
                }
                BuildInvertIndex(*doc);
                count++;
                if (count % 50 == 0)
                {
                    std::cout << "当前已经建立的索引文档：" << count << std::endl;
                }
            }
            return true;
        }

    private:
        DocInfo *BuildForwardIndex(const std::string &line)
        {
            // 1.解析里，字符串切分
            std::vector<std::string> results;
            std::string sep = "\3"; // 行内分隔符
            ns_util::StringUtil::CutString(line, &results, sep);
            // ns_util::StringUtil::CutString(line,&results,sep);
            if (results.size() != 3)
            {
                return nullptr;
            }
            // 2.字符串进行填充到DocIinfo
            DocInfo doc;
            doc.title = results[0];
            doc.content = results[1];
            doc.url = results[2];
            doc.doc_id = forward_index.size(); // 先进行保存id，再插入，对应id久视当前doc在vec中的下标。

            // 3.插入到正排索引的vector
            forward_index.push_back(doc);
            return &forward_index.back();
        }
        bool BuildInvertIndex(const DocInfo &doc)
        {
            // DocInfo
            struct word_cnt
            {
                int title_cnt;
                int content_cnt;
                word_cnt() : title_cnt(0), content_cnt(0) {}
            };
            std::unordered_map<std::string, word_cnt> word_map;
            std::vector<std::string> title_words;
            ns_util::JiebaUtil::CutString(doc.title, &title_words);

            for (auto &s : title_words)
            {
                word_map[s].title_cnt++; // 如果存在就获取，如果不存在就新建
            }

            std::vector<std::string> content_words;
            ns_util::JiebaUtil::CutString(doc.content, &content_words);
            for (auto &s : content_words)
            {
                word_map[s].content_cnt++;
            }
#define X 10
#define Y 1
            for (auto &word_pair : word_map)
            {
                InvertedElem item;
                item.doc_id = doc.doc_id;
                item.words = word_pair.first;
                item.weight = X * word_pair.second.title_cnt + Y * word_pair.second.content_cnt;
                InvertedList &inverted_list = inverted_index[word_pair.first];
                inverted_list.push_back(item);
            }
            return true;
        }
    };
    Index *Index::instance = nullptr;
    std::mutex Index::mtx;
}
